Distributed Operation of the X.500 Directory

Abstract The CCITT/ISO standard “The Directory” defines a major new OSI application and represents a major milestone in the development of large-scale distributed systems. The Standard provides a specification for a distributed global on-line directory. Distributed operation of the Directory is achieved through a complex combination of protocols and the knowledge each component system has of the others. This paper examines the distributed operation of the Directory. It has a threefold purpose: firstly, it gives a comprehensive tutorial on the distributed operation of the Directory; secondly, it shows the rationale behind the design; and thirdly, it provides further insights into various aspects, revealing potential traps and optimisations for implementors. Together the material caters for a range of reader, from those wanting to understand the subject for the first time through to X.500 implementors.